Abstract
The sequence of 415 nucleotides surrounding the transcription termination site for ribosomal RNA in Tetrahymena thermophila has been determined. The positions of the 3'-ends of mature 26S rRNA, pre-26S rRNA and 35S pre-rRNA were localized within this sequence by hybridization of the purified RNA species to be selected DNA fragments, followed by S1 nuclease treatment of the hybrid and a precise sizing of the RNA-protected DNA fragments on sequencing gels. The 35S pre-rRNA population contained molecules with two distinct 3'-ends, one of which is identical to the end of pre-26S and 26S rRNA, while the other corresponds to a position 15 nucleotides further downstream, which is assumed to be the transcription termination site. The non-coding DNA strand contains a cluster of T's at the putative termination site, and several other T clusters are found further downstream. A short inverted repeat sequence is located near the putative termination site within the transcribed region. The possible role of these structures for transcription termination is discussed.